For the unwinding of newsprint from reels in printing presses, such as the widely used Goss Headliner Offset Printing Press, newsprint has been traditionally wound at the newsprint paper manufacturer onto elongate tubular cores to form rolls of newsprint. These newsprint rolls are often stored at the newsprint manufacturer, then shipped to the newspaper printer, often stored at the newspaper printer, and then mounted on stub shafts or chucks in reels of printing presses to be unwound and fed through the printing presses during the printing of newspapers.
The elongate tubular cores in early times were manufactured of wood and in later times have been manufactured of paper having a multi-ply spirally-wound construction. Metal end caps having a longitudinal groove therein have long been utilized on opposite end portions of the core, since early printing presses were axially driven and braked. The metal end caps reinforced the core ends to transmit axial torque and roll weight to the narrow shoulders of the outside surfaces of the printing press reel stub shafts or chucks. The metal end caps were also thought to reinforce the opposite end portions of the core against damage to the end portions of the core and the newsprint roll during storage and shipment.
Later printing presses became peripherally driven and braked and the demand for axial torque diminished; however, the requirement for weight support at the point of Contact of these metal end caps with the narrow shoulders of the stub shafts or chucks of the printing press reels increased over the years due to increased newsprint roll weights and increased newsprint unwinding speeds. The result of such increased newsprint roll weights and unwinding speeds was less effective control of the core in bouncing or vibrating on the reel stub shafts or chucks and thus causing undesirable vibration in the newsprint being unwound and fed into the printing presses.
The usual industry response to this problem, rather than redesign of the newsprint core, has heretofore been to build more sophisticated newsprint roll chucks or stub shafts including web vibration controls, such as air pressure chucks or stub shafts which increasingly "home in" on expiring rolls as the cores retract from the stub shafts or chucks due to deflection and vibration.
This type of newsprint cores having metal end caps did not allow for the cores to be non-returnable by the newspaper printers and the newspaper printers were requested to return all of these cores to the paper manufacturers for reuse in winding additional rolls of newsprint. This created handling problems both with the newspaper printer and with the paper manufacturer.
In recent times, there has been some attempt to provide non-returnable newsprint cores by eliminating the metal end caps on the cores. However, no significant redesign of the core construction was effected after removal of the metal end caps, other than to burnish or grind away a small flat portion at the opposite ends of the paper cores to provide for a contact area for the cores on the narrow shoulders of the outside surfaces of the printing press reel stub shafts or chucks, generally along the lines previously provided by the metal end caps. Due to the increased weight and unwinding speeds of the newsprint rolls, elimination of the metal end caps with this type of core was not found to be satisfactory by most newspaper printers and, thus, attempts at non-returnable newsprint cores have largely been unsuccessful.
As newsprint roll weights increased, damage to the end portions of the tubular core and the newsprint roll during shipping and storage increased. This often occurred as a result of impact on the outside circumference of the newsprint roll, particularly at the ends thereof. The result was that distortion to the metal end caps was duplicated on the inside surface thereof and the metal end caps could not ride up far enough on the shoulder of the printing press reel stub shafts and would consequently bounce and vibrate as the newsprint roll is unwound in the printing press.
Core plugs have been designed and utilized for being inserted into the end portions of the tubular core after winding of the newsprint roll and during shipping and storage to prevent damage to the end portion of the tubular core and to the newsprint roll. These core plugs were removed prior to mounting of the newsprint roll in the reels of the printing presses. Such core plugs were formed of a variety of types of materials, such as wood, plastic or other crush-resistant material. The most common core plugs utilized were generally cylindrical in shape and utilized a centrally located hole therethrough for the insertion of a tool therein to remove the core plug from the core after storage and shipping.
It was found that this centrally located hole for removal of the core plug from the core resulted in a weakened core plug which did not provide all of the core crush resistance desired. More recently, improvements to this construction of a core plug have been suggested, such as disclosed in U.S. Pat. No. 4,484,715, wherein the core plug includes an opening or grooves spaced from the center of thereof and near its remote outer edge for use in removal of the core plug from the core, while increasing crush resistance of the core plug. However, it has been found that this core plug construction with a groove at its outer edge, rather than a centrally located hole, may not provide sufficient core crush resistance in some instances.